Diaphragm, secondary battery, and electric device

Abstract

The invention relates to a diaphragm, a secondary battery and an electric device. The diaphragm comprises a first porous insulating layer, a second porous insulating layer and a middle layer located between the first porous insulating layer and the second porous insulating layer, and the middle layer comprises lithium alloy. The diaphragm can improve the cycle performance of the battery, and especially has a remarkable improvement effect on the cycle performance of a double-electrolyte battery.

Description

Technical Field

[0001] The present application relates to the technical field of secondary batteries, and particularly to a separator, a secondary battery, and an electrical device. Background Art

[0002] The statements herein only provide background information related to the present application and do not necessarily constitute prior art.

[0003] In recent years, with the increasingly wide application range of lithium-ion batteries, lithium-ion batteries are widely used in energy storage power systems such as hydroelectric, thermal, wind, and solar power stations, as well as in multiple fields such as power tools, electric bicycles, electric motorcycles, electric vehicles, military equipment, and aerospace. Due to the great development of lithium-ion batteries, higher requirements are also put forward for their cycle performance, safety performance, rate performance, etc. As the channel for lithium ions to transfer between the positive and negative electrodes in the battery, the influence of the separator on the battery performance cannot be ignored.

[0004] In order for lithium ions to permeate through the separator for transfer, commercial conventional separators mostly adopt a loose porous morphology. However, this also causes substances such as solutes, solvents, and additives in the electrolyte to easily permeate through the separator, thereby having a negative impact on the battery performance, especially the cycle performance. Therefore, the existing porous structure separators still need to be improved. Summary of the Invention

[0005] The present application provides a separator, a secondary battery, and an electrical device to improve the cycle performance of the battery.

[0006] To achieve the above object, a first aspect of the present application provides a separator, including a first porous insulating layer, a second porous insulating layer, and an intermediate layer located between the first porous insulating layer and the second porous insulating layer, where the intermediate layer includes a lithium alloy.

[0007] When the above separator is used in a lithium-ion battery, it can achieve the insertion and extraction of lithium and play a role in transferring lithium ions. Compared with the existing traditional porous structure separators, the intermediate layer of the above separator is denser, which can greatly reduce the probability of other substances except lithium ions permeating through the separator, and can almost completely block other substances except lithium ions from permeating through the separator, achieving the purpose of selectively permeating lithium ions and improving the cycle performance of the battery. Taking charging as an example, lithium ions are extracted from the positive electrode of the battery. Under the action of voltage drive and electrolyte, the lithium ions contact the lithium alloy in the intermediate layer and undergo a lithium alloying reaction. The lithium ions extracted from the positive electrode are inserted into the intermediate layer, and at the same time, the lithium ions in the original lithium alloy are extracted, thereby realizing the transfer of lithium ions. The relevant electrochemical reaction formula is: Li + +e - +X=LiX, LiX - e - =Li ++X, where X is a metal element other than lithium in the lithium alloy, such as silver. Additionally, the first porous insulating layer and the second porous insulating layer of the present application are respectively located on both sides of the intermediate layer, serving as insulation to prevent battery short - circuit.

[0008] In some embodiments of the present application, the intermediate layer comprises one or more of lithium - silver alloy, lithium - germanium alloy, lithium - tin alloy, lithium - zinc alloy, lithium - magnesium alloy, lithium - carbon alloy, and lithium - silicon alloy. Optionally, the intermediate layer comprises lithium - silver alloy, which can further improve the lithium - ion conductivity of the separator.

[0009] In some embodiments of the present application, the mass content of lithium in the lithium alloy is 0.1 wt% - 50 wt%, and optionally 0.5 wt% - 20 wt%. The lithium alloy within the above - mentioned lithium content range, as the intermediate layer, can endow the separator with good lithium - ion conductivity while meeting the necessary conditions for metal alloy formation, thereby further enhancing the battery cycle performance.

[0010] In some embodiments of the present application, the total thickness of the first porous insulating layer and the second porous insulating layer is D, and the thickness of the intermediate layer is d, where 0.004 ≤ d / D ≤ 1.75, and optionally 0.008 ≤ d / D ≤ 0.1. The thinner the intermediate layer, the better the lithium - ion conductivity of the separator; the thicker the intermediate layer, the stronger the mechanical strength of the separator. The thicker the total thickness of the first porous insulating layer and the second porous insulating layer, the better the isolation between the positive and negative electrodes inside the battery, further controlling the short - circuit problem between the positive and negative electrodes of the battery. The thicknesses of each layer within the above - mentioned ratio range can further comprehensively consider the lithium - ion conductivity and mechanical strength of the separator, and at the same time can further improve the energy density of the battery, thereby further enhancing the battery cycle performance.

[0011] In some embodiments of the present application, 2 μm ≤ D ≤ 20 μm, and optionally 5 μm ≤ D ≤ 12 μm; and / or, 0.05 μm ≤ d ≤ 20 μm, and optionally 0.1 μm ≤ d ≤ 1 μm.

[0012] In some embodiments of the present application, the first porous insulating layer comprises a first base film, and the first base film comprises a laminate of any one or more of polyolefin, polyamide, polyester, and their respective derivatives; and / or,

[0013] The second porous insulating layer comprises a second base film, and the second base film comprises a laminate of any one or more of polyolefin, polyamide, polyester, and their respective derivatives. Optionally, the first porous insulating layer further comprises a first inorganic ceramic coating, and the first inorganic ceramic coating is disposed on at least one surface of the first base film. Optionally, the second porous insulating layer further comprises a second inorganic ceramic coating, and the second inorganic ceramic coating is disposed on at least one surface of the second base film.

[0014] In some embodiments of the present application, the lithium-ion conductivity of the separator is >0.1 mS / cm, and optionally >0.3 mS / cm.

[0015] In some embodiments of the present application, the air permeability of the separator is ≥40000 s / 100 mL, and optionally 40000 s / 100 mL to 80000 s / 100 mL.

[0016] The second aspect of the present application further provides a secondary battery, including any one of the separators described in the first aspect above.

[0017] Thus, by using the selective permeable separator of the present application, a transmission channel for lithium ions can be constructed, and at the same time, the transmission of other substances except lithium ions is almost completely blocked, thereby improving the cycling performance of the secondary battery.

[0018] In some embodiments of the present application, the secondary battery further includes a positive electrode plate and a negative electrode plate. The positive electrode plate includes a positive electrode active material, and the positive electrode active material includes lithium manganate.

[0019] In some embodiments of the present application, the secondary battery further includes a first electrolyte disposed between the positive electrode plate and the separator and a second electrolyte disposed between the negative electrode plate and the separator; the first electrolyte and / or the second electrolyte includes one or more of vinylene carbonate, acrylonitrile, xylene, and phenylcyclohexane.

[0020] In some embodiments of the present application, the composition and / or content of the first electrolyte is different from that of the second electrolyte.

[0021] The third aspect of the present application provides an electrical device, including at least one of any one of the separators described in the first aspect of the present application and the secondary battery described in the second aspect of the present application.

[0022] The electrical device of the present application includes the secondary battery provided by the present application, and thus has at least the same advantages as the secondary battery.

[0023] Details of one or more embodiments of the present application are set forth in the following drawings and description. Other features, objects, and advantages of the present application will become apparent from the specification, drawings, and claims. Description of the Drawings

[0024] To better describe and illustrate the embodiments or examples provided in this application, reference may be made to one or more drawings. Additional details or examples used to describe the drawings should not be considered as limiting the scope of any of the disclosed applications, the currently described embodiments or examples, or the best mode of these applications currently understood. Moreover, in all the drawings, the same reference numerals are used to denote the same components. In the drawings:

[0025] Figure 1 Schematic diagram of the structure of a separator according to an embodiment of the present application.

[0026] Figure 2 Schematic diagram of a battery cell according to an embodiment of the present application.

[0027] Figure 3 is Figure 2 Exploded view of the battery cell shown in an embodiment of the present application.

[0028] Figure 4 Schematic diagram of a battery module according to an embodiment of the present application.

[0029] Figure 5 Schematic diagram of a battery pack according to an embodiment of the present application.

[0030] Figure 6 is Figure 5 Exploded view of the battery pack shown in an embodiment of the present application.

[0031] Figure 7 Schematic diagram of an electrical device powered by a secondary battery according to an embodiment of the present application.

[0032] Explanation of reference numerals:

[0033] 1 Battery pack; 2 Upper box body; 3 Lower box body; 4 Battery module; 5 Battery cell; 51 Housing; 52 Electrode assembly; 53 Cover plate; 6 Electrical device; 10 First porous insulating layer; 20 Intermediate layer; 30 Second porous insulating layer. Detailed implementation manners

[0034] Hereinafter, some embodiments of the separator, secondary battery, and electrical device of the present application are described in detail with appropriate reference to the drawings. However, there may be cases where unnecessary detailed descriptions are omitted. For example, there are cases where detailed descriptions of well-known matters and repeated descriptions of actually identical structures are omitted. This is to avoid making the following descriptions unnecessarily lengthy and to facilitate the understanding of those skilled in the art. In addition, the drawings and the following descriptions are provided for those skilled in the art to fully understand the present application and are not intended to limit the subject matter recited in the claims.

[0035] The "range" disclosed in this application can be defined in the form of a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, and the selected lower limit and upper limit define the boundary of a particular range. The range defined in this way can include or exclude the end values. Any end value can be independently included or excluded, and any combination can be made, that is, any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60 - 120 and 80 - 110 are listed for a specific parameter, ranges of 60 - 110 and 80 - 120 are understood to be anticipated. In addition, if the minimum range values 1 and 2 are listed, and if the maximum range values 3, 4, and 5 are also listed, the following ranges are all anticipated: 1 - 3, 1 - 4, 1 - 5, 2 - 3, 2 - 4, and 2 - 5. In this application, unless otherwise stated, the numerical range "a - b" represents an abbreviated representation of any real number combination between a and b, where both a and b are real numbers. For example, the numerical range "0 - 5" means that all real numbers between "0 - 5" are fully listed herein, and "0 - 5" is only an abbreviated representation of these numerical combinations. Additionally, when a certain parameter is expressed as an integer ≥2, it is equivalent to listing the parameter as integers such as 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc. For example, when a certain parameter is expressed as an integer selected from "2 - 10", it is equivalent to listing the integers 2, 3, 4, 5, 6, 7, 8, 9, and 10.

[0036] In this application, when it comes to "multiple", "a variety of", etc., unless otherwise specified, it means greater than 2 or equal to 2 in quantity. For example, "one or more" means one or greater than or equal to two.

[0037] If there is no special instruction, all embodiments and optional embodiments of this application can be combined with each other to form a new technical solution.

[0038] Referring to "embodiment" in this text means that the specific features, structures, or characteristics described in connection with the embodiment can be included in at least one embodiment or implementation manner of this application. The appearance of this phrase at various positions in the specification does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment mutually exclusive with other embodiments. Those skilled in the art explicitly and implicitly understand that the embodiments described herein can be combined with other embodiments. The same understanding applies to the "implementation manner" mentioned in this text.

[0039] Those skilled in the art can understand that in the methods of various embodiments or examples, the written order of each step does not mean a strict execution order that constitutes any limitation to the implementation process. The detailed execution order of each step should be determined by its function and possible internal logic. If there is no special description, all steps of this application can be carried out sequentially or randomly, and preferably sequentially. For example, the method includes steps (a) and (b), which means that the method may include steps (a) and (b) carried out sequentially, or may also include steps (b) and (a) carried out sequentially. For example, it is mentioned that the method may further include step (c), which means that step (c) can be added to the method in any order. For example, the method may include steps (a), (b) and (c), or may also include steps (a), (c) and (b), or may also include steps (c), (a) and (b), etc.

[0040] In this application, in an open technical feature or technical solution described by words such as "containing", "comprising", "including", etc., without other instructions, additional members other than the listed members are not excluded, and it can be regarded as providing both a closed feature or solution composed of the listed members and an open feature or solution that also includes additional members outside the listed members. For example, A includes a1, a2 and a3. Without other instructions, it may also include other members, or may not include additional members, and can be regarded as providing both a feature or solution that "A is composed of a1, a2 and a3" and a feature or solution that "A not only includes a1, a2 and a3, but also includes other members". In this application, without other instructions, A (such as B) means that B is a non-limiting example in A, and it can be understood that A is not limited to B.

[0041] In this application, "optionally", "optional", "option" mean that it can be either present or absent, that is, it refers to any one of two parallel options of "present" or "absent". If "optional" appears multiple times in a technical solution, without special instructions and without contradictions or mutual restrictions, each "optional" is independent of each other.

[0042] In an ideal lithium battery model, only lithium ions can pass through the separator for transmission. The transmission of other substances may have a negative impact on the battery performance. For example, the penetration of anions through the separator will increase the internal polarization of the battery to a certain extent and affect the battery rate performance; some additives are friendly to the positive electrode, but will pass through the separator and affect the negative electrode. At present, the research on blocking separators mainly focuses on ways such as reducing the pores of the separator and filling materials in the separator pores. However, these technical means cannot fundamentally block other substances except lithium ions, and even reduce the ionic conductivity of the separator, increase the polarization of the battery, and make the cycle performance of the battery worse. If it is possible to achieve both the transmission of lithium ions and the blocking of the transmission of other substances except lithium ions, at the same time, ensure the insulation between the positive and negative electrodes, and do not require too much modification to the original commercial separator, and can be very suitably introduced into the existing battery system, this will have a revolutionary impact on the development and application of blocking separators.

[0043] To achieve the above object, an embodiment of the present application provides a separator. Please refer to Figure 1 , which includes a first porous insulating layer 10, a second porous insulating layer 30, and an intermediate layer 20 located between the first porous insulating layer 10 and the second porous insulating layer 30. The intermediate layer 20 includes a lithium alloy.

[0044] When the above separator is used in a lithium-ion battery, it can realize the insertion and extraction of lithium and play a role in transmitting lithium ions. Compared with the existing porous structure separator, the intermediate layer of the above separator is denser, which can greatly reduce the probability of other substances except lithium ions passing through the separator, and can almost completely block other substances except lithium ions from passing through the separator, achieving the purpose of selectively transmitting lithium ions and improving the cycle performance of the battery. Taking charging as an example, lithium ions are extracted from the battery positive electrode. Under the action of voltage and electrolyte, the lithium ions contact the lithium alloy in the intermediate layer and undergo a lithium alloying reaction. The lithium ions extracted from the positive electrode are embedded in the intermediate layer, and at the same time, the lithium ions in the original lithium alloy are extracted, and then the transmission of lithium ions is realized. The relevant electrochemical reaction formula is: Li + +e - +X=LiX, LiX - e - =Li + +X, where X is a metal element other than lithium in the lithium alloy, such as silver. In addition, the first porous insulating layer and the second porous insulating layer of the present application are respectively located on both sides of the intermediate layer to play an insulating role and prevent the battery from short-circuiting.

[0045] In some of the embodiments, the intermediate layer includes one or more of a lithium-silver alloy, a lithium-germanium alloy, a lithium-tin alloy, a lithium-zinc alloy, a lithium-magnesium alloy, a lithium-carbon alloy, and a lithium-silicon alloy. Optionally, the intermediate layer includes a lithium-silver alloy, which can further improve the ionic conductivity of the separator.

[0046] The types of lithium alloys can be tested by methods and instruments well-known in the art. For example, an inductively coupled plasma optical emission spectrometer (ICP) can be used for testing to determine the elemental types.

[0047] In some of these embodiments, the lithium mass content in the lithium alloy of the intermediate layer 20 is 0.1 wt% to 50 wt%, and may be optionally 0.5 wt% to 20 wt%. Understandably, the lithium mass content in the lithium alloy of the intermediate layer 20 can take values such as 0.1 wt%, 0.2 wt%, 0.4 wt%, 0.5 wt%, 0.6 wt%, 0.8 wt%, 1 wt%, 5 wt%, 10 wt%, 20 wt%, 30 wt%, 40 wt%, 50 wt%, and any value therebetween. The lithium alloy within the above range of lithium mass content, as the intermediate layer, can make the separator have good lithium ion conductivity while meeting the necessary conditions for metals to form alloys, thereby further improving the battery cycle performance.

[0048] The lithium mass content in the lithium alloy of the intermediate layer 20 can be tested by methods and instruments well-known in the art. For example, an inductively coupled plasma optical emission spectrometer (ICP) can be used for testing, and the lithium mass content can be obtained through quantitative analysis.

[0049] The total thickness of the first porous insulating layer 10 and the second porous insulating layer 30 is D, and the thickness of the intermediate layer is d. It should be noted that the thicknesses of the first porous insulating layer 10 and the second porous insulating layer 30 can be the same or different, and are preferably the same.

[0050] In some of these embodiments, 0.004 ≤ d / D ≤ 1.75, and may be optionally 0.008 ≤ d / D ≤ 0.1. Understandably, d / D can take values such as 0.004, 0.008, 0.01, 0.05, 0.1, 0.5, 1, 1.5, 1.6, 1.65, 1.7, 1.75, and any value therebetween. The thinner the intermediate layer, the better the lithium ion conductivity of the separator; the thicker the intermediate layer, the stronger the mechanical strength of the separator; the thicker the total thickness of the first porous insulating layer and the second porous insulating layer, the better the isolation between the positive and negative electrodes inside the battery can be guaranteed, and the short circuit problem between the positive and negative electrodes of the battery can be further controlled. The thicknesses of each layer within the above ratio range can further comprehensively consider the lithium ion conductivity and mechanical strength of the separator, and at the same time can further improve the energy density of the battery, thereby further improving the battery cycle performance.

[0051] In some of these embodiments, 2μm ≤ D ≤ 20μm, and optionally 5μm ≤ D ≤ 12μm. Understandably, D can take values such as 2μm, 3μm, 4μm, 5μm, 6μm, 7μm, 8μm, 9μm, 10μm, 11μm, 12μm, 13μm, 14μm, 15μm, 16μm, 17μm, 18μm, 19μm, 20μm and any value therebetween.

[0052] In some of these embodiments, 0.05μm ≤ d ≤ 20μm, and optionally 0.1μm ≤ d ≤ 1μm. Understandably, d can take values such as 0.05μm, 0.08μm, 0.1μm, 0.2μm, 0.5μm, 1μm, 2μm, 5μm, 8μm, 10μm, 12μm, 14μm, 16μm, 18μm, 20μm and any value therebetween.

[0053] The thickness T of the separator can be measured with a micrometer. For example, it can be measured with a micrometer of model Mitutoyo 293-100 with an accuracy of 0.1μm.

[0054] In some of these embodiments, the first porous insulating layer 10 includes a first base film. The first base film is not particularly limited. The first base film can be a single-layer film or a multi-layer composite film, and can include, but is not limited to, one or more of polyolefin, polyamide, polyester, and their respective derivatives. Optionally, the first porous insulating layer further includes a first inorganic ceramic coating. The first inorganic ceramic coating is provided on at least one surface of the first base film. Specific examples of the material of the first inorganic ceramic coating can be enumerated but are not limited to Al2O3, TiO2, SiO2, and combinations thereof.

[0055] In some of these embodiments, the second porous insulating layer 20 includes a second base film. The second base film is not particularly limited. The second base film can be a single-layer film or a multi-layer composite film, and can include, but is not limited to, one or more of polyolefin, polyamide, polyester, and their respective derivatives. Optionally, the second porous insulating layer further includes a second inorganic ceramic coating. The first inorganic ceramic coating is provided on at least one surface of the first base film. Specific examples of the material of the second inorganic ceramic coating can be enumerated but are not limited to Al2O3, TiO2, SiO2, and combinations thereof.

[0056] It should be noted that the constituent materials of the first porous insulating layer 10 and the second porous insulating layer 20 can be the same or different, and are preferably the same.

[0057] In some embodiments, the porosity of the first porous insulating layer 10 is 30% to 50%. In some embodiments, the porosity of the second porous insulating layer 20 is 30% to 50%. It should be noted that the porosities of the first porous insulating layer 10 and the second porous insulating layer 20 may be the same or different, preferably the same.

[0058] In some of these embodiments, the lithium-ion conductivity of the separator is >0.1 mS / cm, and may optionally be >0.3 mS / cm. Understandably, the lithium-ion conductivity of the separator can take values such as 0.1 mS / cm, 0.15 mS / cm, 0.2 mS / cm, 0.25 mS / cm, 0.3 mS / cm, 0.35 mS / cm, 0.4 mS / cm, 0.5 mS / cm, and any value therebetween.

[0059] In some of these embodiments, the air permeability of the separator is ≥40000 s / 100 mL, and may optionally be 40000 s / 100 mL to 80000 s / 100 mL. Understandably, the air permeability of the separator can take values such as 40000 s / 100 mL, 41000 s / 100 mL, 42000 s / 100 mL, 43000 s / 100 mL, 44000 s / 100 mL, 45000 s / 100 mL, 46000 s / 100 mL, 47000 s / 100 mL, 48000 s / 100 mL, 49000 s / 100 mL, 50000 s / 100 mL, 55000 s / 100 mL, 60000 s / 100 mL, 65000 s / 100 mL, 70000 s / 100 mL, 75000 s / 100 mL, 80000 s / 100 mL, and any value therebetween.

[0060] The separator of the present application can be provided, prepared, or formed through commercial purchase and / or processes well-known in the art. For example, the first porous insulating layer and the second porous insulating layer can be obtained through commercial purchase methods, the intermediate layer can be formed through processes such as evaporation coating and magnetron sputtering, and the metal foil can be laminated with the first porous insulating layer and the second porous insulating layer by rolling.

[0061] Another embodiment of the present application provides a secondary battery, including any one of the separators in any of the above embodiments.

[0062] Thus, by using the selective permeable separator of the present application, a transmission channel for lithium ions can be constructed, while almost completely blocking the transmission of substances other than lithium ions, thereby improving the cycle performance of the secondary battery.

[0063] Yet another embodiment of the present application provides an electrical device, including at least one of any of the above separators and the above secondary battery.

[0064] In addition, the secondary battery and the electrical device of the present application will be described below with appropriate reference to the accompanying drawings.

[0065] Normally, a secondary battery includes a positive electrode plate, a negative electrode plate, an electrolyte, and a separator. During the charge and discharge process of the battery, active ions are embedded and extracted back and forth between the positive electrode plate and the negative electrode plate. The electrolyte plays a role in conducting ions between the positive electrode plate and the negative electrode plate. The separator is disposed between the positive electrode plate and the negative electrode plate, mainly to prevent short circuit between the positive and negative electrodes, and at the same time allows ions to pass through.

[0066] Positive electrode plate

[0067] The positive electrode plate includes a positive electrode current collector and a positive electrode active material layer provided on at least one surface of the positive electrode current collector. The positive electrode active material layer includes a positive electrode active material.

[0068] As a non-limiting example, the positive electrode current collector has two surfaces opposite to each other in its own thickness direction, and the positive electrode active material layer is provided on either one or both of the two opposite surfaces of the positive electrode current collector.

[0069] In some embodiments, the positive electrode current collector may be a metal foil or a composite current collector. For example, as the metal foil, aluminum foil may be used. The composite current collector may include a polymer material substrate and a metal layer formed on at least one surface of the polymer material substrate. The composite current collector can be obtained by forming a metal material on the polymer material substrate. In the positive electrode current collector, non-limiting examples of the metal material may include one or more of aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy, etc. In the positive electrode current collector, non-limiting examples of the polymer material substrate may include one or more of substrates such as polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), and polyethylene (PE).

[0070] In some of these embodiments, the positive electrode active material may be a positive electrode active material for batteries known in the art. As a non-limiting example, the positive electrode active material may include one or more of the following materials: lithium-containing phosphates with an olivine structure, lithium transition metal oxides, and their respective modified compounds. However, the present application is not limited to these materials, and other conventional materials that can be used as battery positive electrode active materials can also be used. These positive electrode active materials can be used alone or in combination of two or more. Among them, examples of lithium transition metal oxides may include, but are not limited to, lithium cobalt oxide (such as LiCoO2), lithium nickel oxide, lithium manganese oxide, lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, and their modified compounds, etc. One or more of them. Non-limiting examples of lithium-containing phosphates with an olivine structure may include, but are not limited to, lithium iron phosphate, a composite material of lithium iron phosphate and carbon, lithium manganese phosphate, a composite material of lithium manganese phosphate and carbon, lithium manganese iron phosphate, and a composite material of lithium manganese iron phosphate and carbon. Non-limiting examples of lithium cobalt oxide may include LiCoO2; non-limiting examples of lithium nickel oxide may include LiNiO2; non-limiting examples of lithium manganese oxide may include LiMnO2, LiMn2O4, etc.; non-limiting examples of lithium nickel cobalt manganese oxide may include LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2 (which can also be abbreviated as NCM 333 ), LiNi 0.5 Co 0.2 Mn 0.3 O2 (which can also be abbreviated as NCM 523 ), LiNi 0.5 Co 0.25 Mn 0.25 O2 (which can also be abbreviated as NCM 211 ), LiNi 0.6 Co 0.2 Mn 0.2 O2 (which can also be abbreviated as NCM 622 ), LiNi 0.8 Co 0.1 Mn 0.1 O2 (which can also be abbreviated as NCM 811 ), etc. Non-limiting examples of lithium nickel cobalt aluminum oxide may include LiNi 0.85 Co 0.15 Al 0.05 O2.

[0071] Understandably, during the charge and discharge process of the battery, the insertion and extraction of lithium (Li) and its consumption will occur, and the content of Li in the positive electrode sheet is different when the battery is discharged to different states. In the listing of the positive electrode active materials in this application, unless otherwise specified, the content of Li is the initial state of the material. When the positive electrode active material is applied to the positive electrode sheet in the battery system, after charge and discharge cycles, the content of Li in the positive electrode active material contained in the sheet usually changes. Among them, the content of Li can be measured by molar content, but is not limited thereto. Regarding "the content of Li is the initial state of the material", the initial state of the material refers to the state before being fed into the positive electrode slurry. It can be understood that new materials obtained by appropriately modifying the listed positive electrode active materials are also within the scope of the positive electrode active materials. The aforementioned appropriate modification refers to the acceptable modification methods for the positive electrode active materials, and non-limiting examples include coating modification.

[0072] In the listing of the positive electrode active materials in this application, the content of oxygen (O) is only the theoretical state value, and the release of oxygen from the crystal lattice will cause the molar content of oxygen to change, and the actual content of O will show fluctuations. Among them, the content of O can be measured by molar content, but is not limited thereto.

[0073] In some of the embodiments, the positive electrode active material includes lithium manganate. Manganese dissolution will occur in the lithium manganate material in the battery, and it will shuttle to the negative electrode side in the battery using a traditional separator, which will affect the battery performance. However, the secondary battery of this application can block the shuttle of manganese and improve the cycle performance of this type of battery system.

[0074] In some of the embodiments, the positive electrode active material layer may further optionally include a binder. As a non-limiting example, the binder can include one or more of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorinated acrylate resin.

[0075] In some of the embodiments, the positive electrode active material layer may further optionally include a conductive agent. As a non-limiting example, the conductive agent can include one or more of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0076] In some of these embodiments, the positive electrode sheet can be prepared in the following manner: dispersing the above-mentioned components for preparing the positive electrode sheet, such as the positive electrode active material, the conductive agent, the binder, and any other components, in a solvent to form a positive electrode slurry; coating the positive electrode slurry on at least one surface of the positive electrode current collector, and after processes such as drying and cold pressing, the positive electrode sheet can be obtained. The type of the solvent can be selected from but not limited to any one of the foregoing embodiments, such as N-methylpyrrolidone (NMP). The surface of the positive electrode current collector coated with the positive electrode slurry can be a single surface of the positive electrode current collector or two surfaces of the positive electrode current collector. The surface of the positive electrode current collector coated with the positive electrode slurry can be a single surface of the positive electrode current collector or two surfaces of the positive electrode current collector. The solid content of the positive electrode slurry can be 40wt% - 80wt%. The viscosity of the positive electrode slurry at room temperature can be adjusted to 5000 - 25000 mPa·s. When coating the positive electrode slurry, the coating unit surface density in terms of dry weight (deducting the solvent) can be 15 - 35 mg / cm 2 . The tap density of the positive electrode sheet can be 3.0 - 3.6 g / cm 3 , and can be optionally 3.3 - 3.5 g / cm 3 .

[0077] Negative electrode sheet

[0078] The negative electrode sheet includes a negative electrode current collector and a negative electrode active material layer provided on at least one surface of the negative electrode current collector, and the negative electrode active material layer includes a negative electrode active material.

[0079] As a non-limiting example, the negative electrode current collector has two surfaces opposite to each other in its own thickness direction, and the negative electrode active material layer is provided on any one or both of the two opposite surfaces of the negative electrode current collector.

[0080] In some of these embodiments, the negative electrode current collector can be a metal foil or a composite current collector. For example, as the metal foil, copper foil can be used. The composite current collector can include a polymer material base layer and a metal layer formed on at least one surface of the polymer material substrate. The composite current collector can be obtained by forming a metal material on the polymer material substrate. In the negative electrode current collector, non-limiting examples of the metal material can include one or more of copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy, etc. In the negative electrode current collector, non-limiting examples of the polymer material substrate can include one or more of substrates such as polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), and polyethylene (PE).

[0081] In some of these embodiments, the negative electrode active material may be a negative electrode active material for a battery known in the art. As a non-limiting example, the negative electrode active material may include one or more of the following materials: artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, and lithium titanate, etc. The silicon-based materials may include one or more of elemental silicon, silicon oxides, silicon-carbon composites, silicon-nitrogen composites, and silicon alloys. The tin-based materials may include one or more of elemental tin, tin oxides, and tin alloys. However, the present application is not limited to these materials, and other conventional materials that can be used as the negative electrode active material of the battery may also be used. These negative electrode active materials may be used alone or in combination of two or more.

[0082] In some of these embodiments, the negative electrode active material layer may also optionally include a binder. The binder may include one or more of styrene-butadiene rubber (SBR), polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), polymethacrylic acid (PMAA), and carboxymethyl chitosan (CMCS).

[0083] In some of these embodiments, the negative electrode active material layer may also optionally include a conductive agent. The conductive agent may include one or more of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0084] In some of these embodiments, the negative electrode active material layer may also optionally include other additives, such as thickeners (such as sodium carboxymethyl cellulose (CMC-Na)), etc.

[0085] In some of these embodiments, the negative electrode sheet can be prepared in the following manner: dispersing the above components for preparing the negative electrode sheet, such as the negative electrode active material, the conductive agent, the binder, and any other components, in a solvent (a non-limiting example of the solvent is deionized water) to form a negative electrode slurry; coating the negative electrode slurry on at least one surface of the negative electrode current collector, and after processes such as drying and cold pressing, the negative electrode sheet can be obtained. The surface of the negative electrode current collector coated with the negative electrode slurry can be a single surface of the negative electrode current collector or two surfaces of the negative electrode current collector. The solid content of the negative electrode slurry can be 40wt% - 60wt%. The viscosity of the negative electrode slurry at room temperature can be adjusted to 2000 - 10000 mPa·s. When coating the negative electrode slurry, the coating unit surface density in terms of dry weight (deducting the solvent) can be 75 - 220 g / m 2 The compaction density of the negative electrode sheet can be 1.0 g / cm 3 ~1.8 g / cm 3 。

[0086] Electrolyte

[0087] The electrolyte functions to conduct ions between the positive electrode plate and the negative electrode plate. There are no specific restrictions on the type of electrolyte in this application, and it can be selected according to requirements. For example, the electrolyte can be liquid, gel-like, or all-solid-state.

[0088] In some embodiments, the electrolyte uses an electrolytic solution. The electrolytic solution includes an electrolyte salt and a solvent.

[0089] In some of these embodiments, the electrolyte salt can include one or more of lithium hexafluorophosphate (LiPF6), lithium tetrafluoroborate (LiBF4), lithium perchlorate (LiClO4), lithium hexafluoroarsenate (LiAsF6), lithium bis(fluorosulfonyl)imide (LiFSI), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium trifluoromethanesulfonate (LiTFS), lithium difluorophosphate (LiPO2F2), lithium difluorooxalate borate (LiDFOB), lithium bis(oxalato)borate (LiBOB), lithium difluoro bis(oxalato)phosphate (LiDFOP), and lithium tetrafluorooxalate phosphate (LiTFOP).

[0090] In some of these embodiments, the solvent can include ethylene carbonate (EC, ), propylene carbonate (PC, ), ethyl methyl carbonate (EMC), diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), ethylene carbonate ( ), fluoroethylene carbonate (FEC), methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate, 1,4-butyrolactone, sulfolane, dimethyl sulfone, methyl ethyl sulfone, and diethyl sulfone.

[0091] In some of these embodiments, the electrolytic solution may optionally include additives. For example, the additives can include negative electrode film-forming additives, positive electrode film-forming additives, and can also include additives that can improve certain battery performances, such as additives for improving the overcharge performance of the battery, additives for improving the high-temperature or low-temperature performance of the battery, etc.

[0092] In some of these embodiments, the electrolytic solution includes one or more of vinylene carbonate, acrylonitrile, xylene, and phenylcyclohexane. Additives such as vinylene carbonate, acrylonitrile, xylene, and phenylcyclohexane will produce a shuttle effect and affect the battery performance. The secondary battery of this application can block the shuttle of these additives and improve the cycle performance of this type of battery system.

[0093] In some of these embodiments, the electrolyte includes a first electrolyte and a second electrolyte. The first electrolyte is located between the positive electrode sheet and the separator, and the second electrolyte is located between the negative electrode sheet and the separator. Optionally, the composition and / or content of the first electrolyte is different from that of the second electrolyte. It can be understood that the composition and / or content of the first electrolyte being different from that of the second electrolyte means that the first electrolyte has a different composition from the second electrolyte but the same content; or the first electrolyte and the second electrolyte have the same composition but different contents; or the first electrolyte and the second electrolyte have different compositions and contents. For the secondary batteries in these embodiments, the shuttle effect caused by the different electrolyte compositions and / or contents on both sides of the positive and negative electrodes can also be effectively solved by the secondary battery of the present application, improving the cycle performance of this type of battery system. It should be noted that such batteries have independent chambers in the battery structure, and the first electrolyte and the second electrolyte are located in different independent chambers.

[0094] Understandably, in some embodiments, the first electrolyte and / or the second electrolyte includes one or more of vinylene carbonate, acrylonitrile, xylene, or phenylcyclohexane.

[0095] Separator

[0096] Adopt any separator provided by any of the above embodiments of the present application. It should be noted that the separator of the present application has good chemical stability and mechanical stability.

[0097] In some of these embodiments, the positive electrode sheet, the negative electrode sheet, and the separator can be made into an electrode assembly by a winding process or a stacking process.

[0098] In some of these embodiments, the secondary battery may include an outer package. The outer package can be used to encapsulate the above electrode assembly and electrolyte.

[0099] In some of these embodiments, the outer package of the secondary battery can be a hard shell, such as a hard plastic shell, an aluminum shell, a steel shell, etc. The outer package of the secondary battery can also be a soft package, such as a pouch soft package. The material of the soft package can be plastic. Further, non-limiting examples of the plastic can include one or more of polypropylene, polybutylene terephthalate, and polybutylene succinate, etc.

[0100] The secondary battery includes at least one battery cell. The secondary battery can include 1 or more battery cells.

[0101] In the present application, unless otherwise specified, a "battery cell" refers to a basic unit capable of converting chemical energy and electrical energy into each other. Further, generally, it includes at least a positive electrode plate, a negative electrode plate, and an electrolyte. During the charging and discharging process of the battery, active ions are inserted into and extracted from between the positive electrode plate and the negative electrode plate. The electrolyte plays a role in conducting active ions between the positive electrode plate and the negative electrode plate.

[0102] The present application places no particular limitation on the shape of the battery cell, which can be cylindrical, square, or any other arbitrary shape. For example, Figure 2 is a battery cell 5 with a square structure as an example.

[0103] In some of the embodiments, with reference to Figure 3 , the outer package may include a housing 51 and a cover plate 53. Among them, the housing 51 may include a bottom plate and side plates connected to the bottom plate, and the bottom plate and the side plates enclose to form a receiving cavity. The housing 51 has an opening communicating with the receiving cavity, and the cover plate 53 can be covered on the opening to close the receiving cavity. The positive electrode plate, the negative electrode plate, and the separator may be formed into an electrode assembly 52 through a winding process or a stacking process. The electrode assembly 52 is encapsulated in the receiving cavity. The electrolyte is infiltrated in the electrode assembly 52. The number of electrode assemblies 52 included in the battery cell 5 can be one or more, and those skilled in the art can select according to actual needs.

[0104] The secondary battery can be a battery module 4 or a battery pack 1.

[0105] The battery module includes at least one battery cell. The number of battery cells included in the battery module can be one or more, and those skilled in the art can select a suitable number according to the application and capacity of the battery module.

[0106] Figure 4 is a battery module 4 as an example. With reference to Figure 4 , in the battery module 4, a plurality of battery cells 5 can be arranged in sequence along the length direction of the battery module 4. Of course, they can also be arranged in any other arbitrary manner. Further, the plurality of battery cells 5 can be fixed by fasteners.

[0107] Optionally, the battery module 4 may further include a housing having a receiving space, and a plurality of battery cells 5 are received in the receiving space.

[0108] In some of the embodiments, the above battery module can also be assembled into a battery pack. The number of battery modules included in the battery pack can be one or more, and those skilled in the art can select a suitable number according to the application and capacity of the battery pack.

[0109] Figure 5 and Figure 6 is a battery pack 1 as an example. With reference to Figure 5and Figure 6 In the battery pack 1, a battery box and a plurality of battery modules 4 disposed in the battery box may be included. The battery box includes an upper box body 2 and a lower box body 3. The upper box body 2 can be covered on the lower box body 3 to form a closed space for accommodating the battery modules 4. The plurality of battery modules 4 can be arranged in the battery box in any manner.

[0110] In addition, the present application also provides an electrical device, and the electrical device includes the secondary battery provided by the present application. The secondary battery can be used as the power source of the electrical device or as the energy storage unit of the electrical device. The electrical device may include a mobile device, an electric vehicle, an electric train, a ship, a satellite, an energy storage system, etc., but is not limited thereto. Among them, the mobile device may be, for example, a mobile phone, a laptop computer, etc.; the electric vehicle may be, for example, a pure electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle, an electric bicycle, an electric scooter, an electric golf cart, an electric truck, etc., but is not limited thereto.

[0111] As the electrical device, the secondary battery can be selected according to its usage requirements.

[0112] Figure 7 Shown is an electrical device 6 as an example. The electrical device is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle, etc. In order to meet the high power and high energy density requirements of the electrical device for the secondary battery, a battery pack or a battery module can be adopted.

[0113] As another example of the device, it can be a mobile phone, a tablet computer, a laptop computer, etc. This device usually requires thinness and lightness, and a secondary battery can be used as the power source.

[0114] Hereinafter, embodiments of the present application will be described. The embodiments described below are exemplary and are only used to explain the present application and should not be construed as a limitation of the present application. For those not specified in the embodiments in terms of techniques or conditions, they shall be carried out according to the techniques or conditions described in the literature in the art or according to the product specifications. For reagents or instruments not specified in terms of the manufacturer, they are all conventional products that can be obtained through commercial purchase.

[0115] Embodiment 1

[0116] 1) Preparation of the positive electrode sheet

[0117] The positive electrode active material lithium manganate LiMn2O4, the conductive agent acetylene black, and the binder PVDF are dispersed in the solvent N-methylpyrrolidone in a weight ratio of 93:3:4 and mixed evenly to obtain a positive electrode slurry; the positive electrode slurry is evenly coated on both side surfaces of the positive electrode current collector aluminum foil, and after drying and cold pressing, a positive electrode sheet is obtained, wherein the coating amount per unit area of both sides is 0.27 g / 1540.25 mm 2 .

[0118] 2) Preparation of the negative electrode sheet

[0119] Mix the negative active material graphite, conductive agent acetylene black, and binder styrene-butadiene rubber in a mass ratio of 93:3:4, add deionized water, and obtain a negative electrode slurry under the action of a vacuum mixer; uniformly coat the negative electrode slurry on both sides of the copper foil; dry the copper foil at room temperature and then transfer it to an oven for drying, and then obtain the negative electrode sheet through cold pressing and slitting. The coating amount per unit area on both sides is 0.17 g / 1540.25 mm 2 .

[0120] 3) Separator

[0121] Select two 6-μm-thick polypropylene porous separators. Through a calendering process, a lithium-silver alloy metal foil is laminated on the surface of one of the polypropylene porous separators to form a dense lithium-silver alloy layer about 100 nm thick, and then the other polypropylene porous separator is laminated on the dense lithium-silver alloy layer to form a separator. The dense lithium-silver alloy layer is the intermediate layer. Among them, the mass content of lithium in the lithium-silver alloy is 1%.

[0122] 4) Preparation of the electrolyte

[0123] The organic solvent is a mixed solution containing ethylene carbonate (EC), ethyl methyl carbonate (EMC), and dimethyl carbonate (DMC). Among them, the volume ratio of EC, EMC, and DMC is 1:1:1. In a glove box filled with argon with a water content <10 ppm, the fully dried lithium salt LiFSI is dissolved in the organic solvent and mixed evenly to obtain the electrolyte. Among them, the concentration of the lithium salt is 1 mol / L.

[0124] 5) Preparation of the battery

[0125] Stack the positive electrode sheet, separator, and negative electrode sheet in sequence, with the separator between the positive and negative electrode sheets playing an insulating role. Then wind them into a square bare battery core, put it into an aluminum-plastic film, bake it at 80 °C to remove water, inject 0.3 g of the corresponding non-aqueous electrolyte, seal it, and after processes such as standing, hot and cold pressing, formation, clamping, and grading, obtain the finished battery.

[0126] The preparation methods of the secondary batteries in Examples 2-15 are similar to that of the secondary battery in Example 1, except that: the relevant parameters of the separator are adjusted. The specific parameters are shown in Table 1 below. Among them, in Table 1, D represents the total thickness of the two polypropylene porous membranes, and d represents the thickness of the intermediate layer.

[0127] Comparative Example 1

[0128] The preparation method of the secondary battery in Comparative Example 1 is similar to that of the secondary battery in Example 1, except that: the separator is a 12-μm-thick polypropylene porous separator.

[0129] Test method

[0130] 1. Battery cycle life test

[0131] The test is carried out in a constant temperature environment of 25°C. The process is as follows: Stand still for 5 minutes, discharge at 0.5C (75 mA) until 3V, stand still for 5 minutes, then charge at 1 / 3C to 4.3V, and then perform constant voltage charging at 4.3V until the current ≤ 0.05 mA. Stand still for 5 minutes, and then discharge at 1 / 3C to 3V. The discharge capacity at this time is the initial discharge capacity, denoted as D0. Subsequently, perform cyclic tests in the range of 3 - 4.3V according to the above process, record the capacity value Dn (n = 1, 2, 3...) every week. When the capacity Dn ≤ 80% * D0, record the cycle number n as the cycle life.

[0132] 2. Separator lithium-ion conductivity test

[0133] The separator prepared in step 3) of the above example is punched into small round pieces with a diameter of 22 mm, and the separator thickness h is measured and recorded. The punched separator and a 20 mm steel sheet are encapsulated in a button cell to assemble a steel-steel symmetric cell. The electrochemical impedance spectroscopy method of a Solartron 1470E CellTest multi-channel electrochemical workstation is used for testing. The test voltage can be 10 mV, and the test frequency can be 0.1 Hz - 100 K Hz. A Nyquist diagram is plotted; the obtained Nyquist diagram is analyzed by using the equivalent circuit curve fitting method with Zview software, and the intersection of the straight line and the horizontal axis is denoted as R. The ionic conductivity is calculated using the formula λ = h / RS (where λ represents ionic conductivity, h represents separator thickness, R represents ionic resistance, and S represents the cross-sectional area of the small round piece).

[0134] 3. Separator air permeability

[0135] The separator is cut into appropriate sizes, and a separator air permeability tester is used to test the air permeability of the separator. The test is carried out according to the content in the standard GB / T 36363 - 2018 "Polyolefin Separator for Lithium-Ion Batteries". The specific method is as follows:

[0136] At a temperature of (23 ± 2)°C and a relative humidity of 50% ± 10%, cut 3 samples of the separator at intervals of 150 mm longitudinally on the separator membrane. Use a permeameter to test the air permeability of the 3 samples. The pressure applied by the permeameter is 1.21 kPa, and the time taken for 100 mL of air to pass through the separator membrane is measured. Take the average value of the test results of the 3 samples as the air permeability of the separator membrane.

[0137] The above test results are shown in Table 1.

[0138] Table 1

[0139]

[0140] As can be seen from Table 1, compared with Comparative Example 1, the lithium-ion conductivity of the diaphragms provided in Examples 1 to 15 of the present application can meet the standards of commercial batteries, and the air permeability is very low, indicating that it can achieve the transmission of lithium ions and has a strong blocking ability for substances other than lithium ions. The cycle performance of the batteries has been effectively improved.

[0141] The descriptions of the above embodiments tend to emphasize the differences between the embodiments. Their similarities or similarities can be referred to each other. For the sake of brevity, they will not be repeated herein.

[0142] It should be noted that the present application is not limited to the above embodiments. The above embodiments are only examples, and embodiments having the same composition and the same effect as the technical idea within the technical solution scope of the present application are included in the technical scope of the present application. In addition, within the scope not departing from the gist of the present application, various modifications that can be conceived by those skilled in the art to the embodiments and other ways constructed by combining some of the constituent elements of the embodiments are also included in the scope of the present application.

Claims

1. A separator, characterized in that, It includes a first porous insulating layer, a second porous insulating layer, and an intermediate layer located between the first porous insulating layer and the second porous insulating layer, and the intermediate layer includes a lithium alloy.

2. The diaphragm according to claim 1, characterized in that, The intermediate layer includes one or more of a lithium-silver alloy, a lithium-germanium alloy, a lithium-tin alloy, a lithium-zinc alloy, a lithium-magnesium alloy, a lithium-carbon alloy, and a lithium-silicon alloy.

3. The diaphragm according to claim 1 or 2, characterized in that, The mass content of lithium in the lithium alloy is 0.1 wt% to 50 wt%.

4. The diaphragm according to any one of claims 1 to 3, characterized in that The mass content of lithium in the lithium alloy is 0.5 wt% to 20 wt%.

5. The diaphragm according to any one of claims 1 to 4, characterized in that, The total thickness of the first porous insulating layer and the second porous insulating layer is D, and the thickness of the intermediate layer is d, where 0.004 ≤ d / D ≤ 1.

75.

6. The diaphragm according to claim 5, wherein, 0.008 ≤ d / D ≤ 0.

1.

7. The diaphragm according to claim 5 or 6, characterized in that, 2 μm ≤ D ≤ 20 μm; and / or, 0.05 μm ≤ d ≤ 20 μm.

8. The diaphragm according to any one of claims 5 to 7, characterized in that, 5 μm ≤ D ≤ 12 μm; and / or, 0.1 μm ≤ d ≤ 1 μm.

9. The separator according to any one of claims 1 to 8, characterized in that, The first porous insulating layer includes a first base film, and the first base film includes a laminate of any one or more of polyolefin, polyamide, polyester, and their respective derivatives; and / or, The second porous insulating layer includes a second base film, and the second base film includes a laminate of any one or more of polyolefin, polyamide, polyester, and their respective derivatives.

10. The separator according to any one of claims 1 to 9, characterized in that, The lithium ion conductivity of the separator is > 0.1 mS / cm.

11. The separator according to any one of claims 1 to 10, characterized in that, The lithium ion conductivity of the separator is > 0.3 mS / cm.

12. The diaphragm according to any one of claims 1 to 11, characterized in that, The air permeability of the separator is ≥ 40000 s / 100 mL.

13. The diaphragm according to any one of claims 1 to 12, characterized in that, The air permeability of the separator is 40000 s / 100 mL to 80000 s / 100 mL.

14. A secondary battery, characterized in that, It includes the separator according to any one of claims 1 to 13.

15. The secondary battery according to claim 14, wherein The secondary battery further includes a positive electrode plate and a negative electrode plate. The positive electrode plate includes a positive electrode active material, and the positive electrode active material includes lithium manganate.

16. The secondary battery according to claim 14 or 15, characterized in that, The secondary battery further includes a first electrolyte disposed between the positive electrode plate and the separator and a second electrolyte disposed between the negative electrode plate and the separator; the first electrolyte and / or the second electrolyte includes one or more of vinylene carbonate, acrylonitrile, xylene, or phenylcyclohexane.

17. The secondary battery according to claim 16, characterized in that, The composition and / or content of the first electrolyte is different from that of the second electrolyte.

18. An electrical device, characterized in that, It includes at least one of the separator according to any one of claims 1 to 13 and the secondary battery according to any one of claims 14 to 17.

Images